The 20-year-old, who is ranked 52 in the world, hit 25 winners to Djokovic's 12 and the Serbian star, who will attempt to win a third consecutive Australian Open later this month, admitted that he needed more time to get to grips with conditions after arriving in Perth just a few days ago.

"I knew I was coming here to Australia very late and it takes me time to get used to it," Djokovic told reporters.

"I know I am not close to my maximum, but I expected that. I was always on the back foot and he was the better player."

Simon, who reached the semifinals in Brisbane last year, will play Marcos Baghdatis in the next round after the Cypriot defeated sixth-seeded German Florian Mayer 6-4 6-2.

Japan's Kei Nishikori reached the last eight thanks to a 6-3 6-3 win over Spain's Tommy Robredo, while Alexandr Dolgopolov of Ukraine progressed when Finland's Jarkko Nieminen retired due to a migraine with the Ukrainian ahead 6-2 4-1.